We all know the old adage "you're not really playing until you've house-ruled that game".

I'm curious: what house rules do you use in your M&M games?

Examples from games I've run:

* Fantasy games on the silver piece standard (more realistic to the Medieval theme than having rivers of gold everywhere).

* Not worrying about power level limits during the course of play (if the players are cunning enough to get their hands on Baron von Doomkrieger's Thule-Ray, and figure out how to work it without destroying it or themselves in the process, they're entitled to get at least a few shots off for their trouble).

* Knowledge (Technology) can substitute for the Computers skill to operate all sorts of devices and machinery (it's kinda redundant that they're 2 separate skills, considering the overlap in real life).

* Proficiency is determined by character background (soldier trained w/ assault rifle, farmboy knows how to use a shotgun, knight familiar w/ swords & lances, etc).Picking up an unfamiliar weapon means -4 to hit (or armor penalties for armor). It takes 1 month (4 7-day weeks) to gain proficiency. After each week of regular use (minimum 10 hours per week), reduce penalty by 1 and eventually negate it.

I've houseruled the heck out of combat until it's 2/3 M&M and 1/3 Pathfinder. I use CMB/CMD from Pathfinder for maneuvers, Hit Points for damage (but not the Mastermind Manual HP rules, which I don't care for), and quite a few modifications to Feats (new Feats, unavailable Feats, modified Feats), mostly due to the combat changes.